In automotive applications, which are subjected to constantly rising demands with regard to cost reduction and efficiency maximisation, the aim is to achieve increasingly reduced pump construction sizes, or to flully omit the use of cooling and lubricating oil pumps in the drive train. Thus, in addition to the drag moments, it is possible to reduce system costs, construction space and weight and to achieve acoustic benefits. The use of the centrifugal force effect of wetted rotating components allows such pumpless constructions. However the effectively usable delivery volume flow here is substantially reduced (e.g., by a factor of 10).
In a friction plate clutch as described in German Patent Publication DE 102006034154 A1, the cooling and lubricating oil is supplied to the clutch pack under the effect of centrifugal force, through radial bores in the clutch hub which are distributed over the periphery. Due to the oil supply which is restricted in the axial direction because of the construction, in particular with a greatly reduced oil volume flow, it is not possible to guarantee an even distribution over the plate pack in the longitudinal direction. This undesirable effect is amplified by the centrifugal force effect which rises with the square of the absolute rotation speed. The friction faces located spatially further away from the supply bores are thus supplied with significantly less oil. The result is restricted usability, i.e., a lower rated power of the clutch as a result of the increased thermal load on the friction faces with reduced supply. A further restriction resulting from inadequate oil supply is the tendency to the occurrence of adhesion slip effects, with the associated acoustic disadvantages.
Initial approaches were aimed at arranging the supply bores offset in the axial direction, which however leads to reduced wetting of the friction faces in the peripheral direction. An additional increase in the number of supply bores does not have a positive effect because of the limited oil volume flow. Also restrictions occur in relation to production and strength, which are reflected in disproportionately high unit costs.
U.S. Pat. No. 4,971,184 discloses a roller overrun clutch with insert parts which are integrated constructionally in the clutch hub. The hub production is adapted and the hub contains radial supply bores which expand conically radially towards the outside. The oil distribution is improved, but a reduced supply to the friction faces further away from the supply bore in the axial direction cannot be prevented with the overall low supply volume flow. In addition, for construction reasons the hub has relatively large areas of weakening.